This invention relates to excavation cutting tools, and more particularly to a rotatable cutting tool and tool holder assembly wherein the rotatable cutting tool and tool holder assembly possesses an improved design so as to provide for improved performance and wear characteristics.
Excavation cutting tool assemblies to impinge earth strata (such as, for example, asphaltic roadway material or ore bearing or coal bearing earth formations or the like) typically comprise a cutting tool, sometimes referred to as a cutting bit or chisel, rotatably mounted within a cutting tool holder, sometimes referred to as a cutting tool sleeve, bit holder, bit sleeve, or chisel holder. In such assemblies, the cutting tool holder is mounted within a support block. The support block in turn is mounted onto a drum or other body, typically by welding, which in turn is driven by a suitable power means. When a number of such support blocks carrying respective cutting tool holders and cutting tools are mounted onto a drum or other body, and the drum or other body is driven, the cutting tools will engage and break up the material which is sought to be mined or removed. The general operation of such mining, road milling, or other such like machines is well known in the art.
Various types and designs of rotatable cutting tools have heretofore been used to impinge earth strata. Generally speaking, known types of rotatable cutting tools have an elongate cutting tool body, typically made from steel, and include a hard tip (or insert) affixed to the cutting tool body at the axial forward end thereof. The hard tip is typically made from a hard material such as, for example, cemented (cobalt) tungsten carbide.
As can be appreciated, during operation the entire rotatable cutting tool and tool holder is typically subjected to a variety of extreme cutting forces and stresses in an abrasive and erosive environment. It would be undesirable for the cutting tool body to prematurely wear or fail, whether it is through catastrophic fracture or the like or through abrasive or erosive wear. In such a circumstance, the rotatable cutting tool would have to be replaced prior to the normally scheduled time for replacement. Further, the premature failure of the rotatable cutting tool or the tool holder would negatively impact the cutting or milling efficiency of the overall earthworking apparatus. It thus becomes apparent that it is important that the cutting tool and tool holder possess the requisite design and strength to maintain its integrity during the intended useful life.